This invention relates generally to an electrophotographic printing, and more particularly, a multiple blade holder for removing particles adhering to the photoconductive member.
In the process of electrophotographic printing, a photoconductive surface is charged to a substantially uniform potential. The photoconductive surface is imagewise exposed to record an electrostatic latent image corresponding to the informational areas of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, a developer material is transported into contact with the electrostatic latent image. Toner particles are attracted from the carrier granules of the developer material onto the latent image. The resultant toner powder image is then transferred from the photoconductive surface to a sheet of support material and permanently affixed thereto.
This process is well known and useful for light lens copying from an original and printing applications from electronically generated or stored originals, and in ionography.
In a reproduction process of the type as described above, it is inevitable that some residual toner will remain on the imaging (i.e. photoreceptive, photoconductive) surface after the toner image has been transferred to the sheet of support material (e.g. paper). It has been found that with such a process that the forces holding some of the toner particles to the imaging surface are stronger than the transfer forces and, therefore, some of the particles remain on the surface after transfer of the toner image. In addition to the residual toner, other particles, such as paper debris (i.e. Kaolin, fibers, clay), additives and plastic, are left behind on the surface after image transfer. (Hereinafter, the term "residual particles" encompasses residual toner and other residual particles remaining after image transfer.) The residual particles adhere firmly to the surface and must be removed prior to the next printing cycle to avoid its interfering with recording a new latent image thereon.
Various methods and apparatus may be used for removing residual particles from the photoconductive imaging surface. hereinbefore, a cleaning brush, a cleaning web, and a cleaning blade have been used. Both cleaning brushes and cleaning webs operate by wiping the surface so as to affect transfer of the residual particles from the imaging surface thereon. After prolonged usage, however, both of these types of cleaning devices become contaminated with toner and must be replaced. This requires discarding the dirty cleaning devices. In high-speed machines this practice has proven not only to be wasteful but also expensive.
The shortcomings of the brush and web made way for another now prevalent form of cleaning known and disclosed in the art--blade cleaning. Blade cleaning involves a blade, normally made of a rubberlike material (i.e. polyurethane) which is dragged or wiped across the surface to remove the residual particles from the surface. Blade cleaning is a highly desirable method, compared to other methods, for removing residual particles due to its simple, inexpensive structure. However, there are certain deficiencies in blade cleaning which are primarily a result of the frictional sealing contact that must occur between the blade and the surface. This frictional sealing contact often leads to blade failure and as a result requires blade replacement.
One problem in the use of such cleaning blade systems for cleaning moving xerographic photoreceptor imaging surfaces of imaging material has been in the mounting or support of the blade, particularly with compressible elastomeric blades. If the blade is compressed, or not completely linearly supported at its mounting edge it may not uniformly engage the imaging surface being repeatedly rotated past the blade edge. This can cause localized cleaning failures causing streaks on the copies, or total cleaning failures as by blade "tuck-under".
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,989,047 to Jugle et al. discloses an apparatus for cleaning an electrophotographic printer imaging surface. The cleaning apparatus includes a primary cleaner device and a secondary cleaning member. The secondary cleaning apparatus consists of a blade holder pivotally connected to the housing that holds a cleaning blade in frictional contact with the imaging surface.
U.S. Pat. No. 4,640,608 to Higaya et al. discloses an apparatus for cleaning a photoconductive surface. The cleaning apparatus includes a blade holder that detachably holds a cleaning blade between two members that are fastened together.
U.S. Pat. No. 4,083,633 to Shanly discloses a blade cleaning holder. One edge of a blade mounted within a blade retaining channel with opposing generally parallel walls spaced apart by a distance slightly greater than the thickness of the blade to provide unobstructed ingress of the cleaning blade mounting edge against a linear base of the channel without compression of the blade. The blade mounting channel has an arcuate intermediate bend resiliently bending the cleaning blade with the channel sufficiently to cause the cleaning blade to resiliently frictionally engage both walls of the channel to frictionally retain the blade and to seal the channel from the image developer material.
U.S. Pat. No. 3,854,162 to Russell discloses a doctor blade holder having a pair of holder members which retain the back edge of a doctor blade between them. One member exerts resilient pressure on the blade to urge it toward the other member through a resilient yieldable strip mounted thereon, the arrangement providing desirable flexibility for the blade and also providing sealing.